Embodiments of the present invention relate to a semiconductor device, and more particularly, to a semiconductor device in which a wall oxide film (also called a sidewall oxide film) is formed to have different thicknesses depending on the location of the sidewall, and a method for forming the same.
As the degree of integration of semiconductor devices increases, the area of a pattern formed over an active region of a semiconductor substrate has been reduced, and the area of a device isolation region formed to prevent the occurrence of electric connection between patterns has been reduced.
A conventional device isolation region had been formed through a local oxidation of silicon (LOCOS) process. As the device isolation region has been gradually reduced in size, a shallow trench isolation (STI) process capable of forming a superior small-sized device isolation region has been developed as an alternative to the LOCOS process.
In the STI process, after a trench having a predetermined depth is formed in a semiconductor substrate, an insulation material is deposited to fill the trench, and then any unnecessary insulation film is removed through a CMP process. As a result, a device isolation region for electrically isolating active regions from each other is formed.
However, as a design rule is gradually reduced, the aspect ratio of a trench is gradually increased, such that a wall oxide film formed over a sidewall of a device isolation trench becomes thinner in thickness.
In addition, as a gate of the semiconductor device is repeatedly turned on/off, a disturbance may be caused by the voltage applied to the gate for the on/off operation. This disturbance may manifest in different ways depending on the location of the gate. For example, a disturbance caused by a neighbor gate (NG), which is shared by neighboring active regions, is different from a disturbance caused by a passing gate (PG), which is formed to pass by an active region.
As a result, a method for solving both NG-based disturbances and PG-based disturbances is in demand.